Lifting devices, in particular cranes, mobile or crawler cranes as well as tower cranes or cable excavators, can be configured in various set-up variants. A load to be lifted is attached to the hoisting cable of a crane or excavator, with the hoisting cable being guided by a guiding means over the boom head up to the drive of the hoisting cable in the form of a cable winch. At this point, numerous variation possibilities are available for guiding the hoisting cable via the boom. For example, the hoisting cable can be guided at the pulley head itself over the boom or over a mast nose attached to the boom end or at various further points of a boom extension, such as, e.g., a folding tip, a luffing tip or a fixed tip. At each of these points, a load including stop means and hook block thus can be lifted.
During retraction of the hoisting cable by the respective cable winch it must be ensured that the hoisting height of the cable is limited such that a crane hook arranged at the hoisting cable or a hook block arranged at the same is not drawn into the cable guide rollers of the guiding means. Retracting the hoisting cable beyond the maximum allowed hoisting height may lead to a damage of the cable guide rollers or even to a rupture of the hoisting cable or the hook block and hence to the load falling down.
To prevent the above-mentioned problems, the actual hoisting height of the hoisting cable or the load must be controlled continuously at the respective guiding means and be communicated to a control unit provided for controlling the crane or excavator operation. A further difficulty consists in that the various guiding means arranged at the crane or excavator may be designed to be usable for simultaneously lifting more than one load. Consequently, the safe operation must be monitored by more than one cable winch.
One method for monitoring the hoisting height of the hoisting cable provides for mounting a so-called hoisting limit switch to each individual guiding means. The function of a hoisting limit switch known from the prior art provides that a weight is longitudinally movably guided on a hoisting cable and attached to the hoisting limit switch via a connecting means. When the stop means of the hoisting cable disallowedly approaches the boom or boom head, the weight is lifted by the stop means on the hoisting cable and the connecting element of the hoisting limit switch is relieved, whereby the hoisting limit switch is actuated and for example interrupts the drive of the hoisting cable. In general, the hoisting limit switches known from the prior art are configured as reed limit switch, Hall switch, inductive switch or as mechanically contacted limit switch. Said switches are largely based on magnetic action principles and are sensitive to strong interfering fields as may occur, e.g., in electroplating plants.
A disadvantage of the above-mentioned monitoring systems for lifting devices consists in that on each guiding means a monitoring element in the form of a hoisting limit switch must always firmly be mounted. However, in such lifting devices only so many guiding means actually can be utilized as drives are present in the form of winches. Thus, in a lifting device with two winches and five guiding means three monitoring elements always remain unused.
Upon actuation of a monitoring element in the form of a hoisting limit switch, the function of the controller of the lifting device is to regulate the drives of the associated hoisting cable (winch). Although the controller clearly knows the position of the respective hoisting limit switch, the controller has no information as to which hoisting cable is actually guided by which winch at the respective hoisting limit switch. This input must be made by the crane operator before operating the crane and thus is susceptible to errors. Only when the crane operator deliberately actuates one winch only and moves the same into the hoisting limit switch, can the controller safely know about the allocation between winch, hoisting cable and hoisting limit switch. Current solutions known from the prior art provide that all winches must be stopped at the same time upon actuation of a hoisting limit switch, independent of which of these actually have exceeded the maximum allowed hoisting height of their driven hoisting cable.
Therefore, it is the object of the present disclosure to provide a lifting device which provides an improved monitoring system of the hoisting cable. Furthermore, it is the object of the present disclosure to disclose a hoisting limit switch which provides an improved possibility for monitoring the hoisting cable and can be used in such lifting device.
This object is solved by a hoisting limit switch for limiting the maximum allowed hoisting height of a hoisting cable. The limit switch includes a read-write device for reading and writing data, and a means from which the operating condition of the hoisting limit switch can be read out by the read-write device. Said means includes information characterizing the operating condition of the hoisting limit switch. For example, the means can include information which describes an allowed operating condition of the hoisting limit switch, which requires that a load attached to the hoisting cable does not exceed a maximum allowed hoisting height. When the maximum allowed hoisting height is reached or exceeded, which involves a risk of destruction of the guiding means, said means indicates a forbidden operating condition. Upon occurrence of a forbidden operating condition certain protective measures can be taken by the hoisting limit switch.
In addition, the read-write device also offers the possibility of reading out data which go beyond the above-mentioned content or to write any desired data onto the means or further receiving elements. Further data to be read out via the read-write device can include, e.g., information on the place of use of the hoisting limit switch. It is also conceivable that during assembly of the hoisting limit switch of the present disclosure the read-write device can write data into a receiving means present at the place of use, which data are a fundamental prerequisite for a reliable functionality of the hoisting limit switch.
Advantageously, the means comprises two transponders which communicate the respective operating condition of the hoisting limit switch to the read-write device. When the first transponder is positioned in the reading area of the read-write device, information is provided which characterizes the allowed operating condition of the hoisting limit switch. By contrast, a second transponder positioned in the reading area of the read-write device leads to the fact that a forbidden operating condition is read out and predefined measures can be taken by the hoisting limit switch of the present disclosure. Particularly preferably, either the first or the second transponder or both transponders are located in the reading area of the read-write device, so that a malfunction of the hoisting limit switch can be recognized as soon as no transponder is detected in the reading area of the read-write device. This is the case for example with a defective read-write device. Thus, a failure of the read-write device also is detectable. When both transponders are located in the reading and writing area of the read-write device, this exactly symbolizes the condition of the transition between allowed and forbidden operating condition. Thus, state transitions can be detected particularly early and measures can be taken. Only a solution with transponders, in particular two transponders, can ensure the high degree of safety of the hoisting limit switch.
Advantageously, the two transponders are mounted one beside the other on a movably guided carrier. The carrier is connected with the hoisting cable at the place of use by suitable means, so that a mechanical action can be transmitted to the movably guided carrier via the hoisting cable, which leads to a displacement of the transponders. In the allowed operating condition, the movably guided carrier preferably is positioned such that the first transponder is located in the reading area of the read-write device. When the hoisting cable reaches a forbidden maximum hoisting height, the hoisting cable acts on the movably guided carrier such that the carrier is displaced and the second transponder enters into the reading area of the read-write device.
It can be provided that the read-write device is configured such that various transponders, which are distributed in several directions, are detectable and readable and/or writable. Consequently, the read-write device has at least two different reading and writing areas, in which suitable means, in particular transponders, are readable and writable.
It is particularly expedient that the hoisting limit switch includes a transponder which is arranged externally in direct vicinity of the hoisting limit switch and is readable and/or writable by means of the read-write device. It is conceivable that such external transponder is already preassigned with data, which upon incorporating the external transponder into the reading and writing area of the read-write device are readable or writable from or into the same. For example, the external transponder is firmly fixed at a possible position of use of the hoisting limit switch. During assembly of the hoisting limit switch, the externally arranged transponder is moved into the reading and writing area of the read-write device, whereby important data for operation of the hoisting limit switch can be read out from the externally arranged transponder.
Advantageously, a means for connection to a bus system for transmitting data is provided on the hoisting limit switch. Consequently, the hoisting limit switch can be used in a system comprising a plurality of individual hoisting limit switches of the present disclosure, and the respective operating conditions of the individual hoisting limit switches of the present disclosure can be transmitted to a central control unit via the bus system. It is also conceivable that via the bus system information on the operation is supplied to the individual hoisting limit switches.
It is also possible that information on the precise mounting position of the hoisting limit switch of a lifting device can be transmitted.
To measure the allowed maximum hoisting height of a hoisting cable, it is provided that the hoisting limit switch includes a weight which can longitudinally movably be mounted on a hoisting cable of a lifting device and is attachable or attached to the hoisting limit switch by means of a connecting element. The use of a longitudinally guided weight on the hoisting cable is known from the hoisting limit switches known from the prior art. In the hoisting limit switch of the present disclosure, the weight longitudinally movably guided on the hoisting cable acts on the means, in particular the two transponders, via the connecting means such that upon relieving the weight a forbidden operating condition can be read out by the read-write device.
In a preferred embodiment of the hoisting limit switch of the present disclosure, the same includes a quick-assembly device. The same provides for releasably and particularly flexibly mounting the hoisting limit switch to the desired place of use.
It is conceivable that the quick-assembly device is firmly fixed at the place of use or already integrated in the component at the place of use of a lifting device and the externally arranged transponder is integrated in the same. It is imaginable that inside the externally arranged transponder data are stored which contain information on the precise place of use. In particular, the externally arranged transponder is located inside the quick-assembly device during assembly of the hoisting limit switch in the reading and writing area of the read-write device. Fixing the quick-assembly device at the place of use offers a constructive possibility for converting existing cranes to the solution in accordance with the present disclosure. Preferably, the quick-assembly device is already integrated in the component of a corresponding crane.
The present disclosure furthermore relates to a lifting device, in particular a crane or cable excavator, comprising at least two different guiding means for at least one hoisting cable for lifting a load, wherein at least one winch is provided for driving the at least one hoisting cable. In accordance with the present disclosure, the lifting device includes at least one sensor device in direct vicinity of each of the at least two guiding means, wherein each sensor independently detects its mounting position. During the crane operations, a load preferably is unilaterally attached to the end of the hoisting cable or preferably the hoisting cable is directed about a deflection pulley at a hook block and at its end attached to the boom by means of a lock or the like. Driving the hoisting cable is effected via a cable winch, wherein the hoisting cable is selectively guided over the boom by one of the guiding means. Crane configurations with a plurality of cable winches are conceivable, which drive various hoisting cables each guided by different guiding means.
The sensors used monitor the operating condition of the lifting device at the respective guiding means. By a sensor automatically detecting its mounting position it is ensured that a reliable and automatic allocation of the sensor to the respective guiding means is effected. By contrast, lifting devices known from the prior art require that an allocation of sensor and guiding means is effected manually by the operator of the lifting device. However, this involves a risk potential hard to assess, which is solved efficiently by the present disclosure.
Particularly preferably, the sensors are releasably mountable or mounted at the respective mounting position. This offers the advantage that sensors need only be mounted at those guiding means which are actually required during operation of the crane. By automatically detecting its own position, the sensor can selectively be positioned at one of the existing guiding means of the lifting device, with the allocation to the guiding means being effected independently due to the position detection of the sensor. By means of this variant of the lifting device in accordance with the present disclosure, the correct allocation of winch, hoisting cable and sensor is simplified considerably. Appreciable risks which can result from a faulty configuration of the sensors can be limited to a minimum.
Expediently, the sensors are designed such that they metrologically detect the position of the hoisting cable, in particular the exceedance of the maximum allowed hoisting height of the hoisting cable, at the guiding means. Hence, the maximum allowed hoisting height of a hoisting cable of the lifting device in accordance with the present disclosure can be monitored and definable measures possibly can be taken when this height is exceeded. Furthermore, it can separately be detected for each individual guiding means whether the correspondingly guided hoisting cable of the individual guiding means has reached a critical maximum hoisting height.
In a particularly advantageous aspect of the present disclosure a control unit is provided in the lifting device, which is connectable or connected with at least one or all sensors. In this way, all or part of the metrologically detected sensor data can be transmitted to the central control unit and be evaluated by the same. In accordance with the present disclosure, it is known to the control unit which sensors are positioned on which guiding means and are responsible for monitoring the same.
It is conceivable that the control unit receives data from at least one sensor, such as the serial number of the lifting device component on which the sensor is arranged and/or the current hoisting cable position and/or an address assigned to the mounting position and/or geometrical data of the lifting device component, such as mass and geometrical data of the component or also the coordinates of the center of gravity.
It is also possible that the control unit transmits data to the sensors. These data can relate, e.g., to the load spectrum.
Expediently, at least one of the sensors comprises a hoisting limit switch according to any of embodiments I to XXII (vide infra). The read-write device of the hoisting limit switch according to any of embodiments I to XXII hence is in constant communication with said control unit of the lifting device. The read-write device on the one hand pursues the object to read out the current operating condition of the hoisting limit switch and transmit the same to the control unit. On the other hand, it is one of the objects of the hoisting limit switch to determine the current mounting position of the hoisting limit switch and to transmit data, such as the serial number of the steel component to which the hoisting limit switch is attached, the coordinates of the center of gravity, mass and geometrical data of the component and an unambiguous address assigned to the hoisting limit switch, to the control unit, whereby an exact allocation of the hoisting limit switch to the guiding means, the hoisting cable guided over the same and the winch driving the hoisting cable is possible. Furthermore, it is possible that during use of the crane data can be written into the externally arranged transponder by means of the read-write device.
The central control unit of the lifting device of the present disclosure, which receives the data of the sensors connected with the same, is configured such that the at least one winch can be actuated in dependence on the data transmitted to the control unit. For example, the operation of the winch can be deactivated if the sensors detect an exceedance of the maximum allowed hoisting height of a hoisting cable.
It is particularly expedient that the control unit is configured such that several winches can be actuated separately in case of need. Due to the inventive allocation of the sensors to the respective guiding means exactly one winch responsible for the operation of the hoisting cable can be switched off in case of need, i.e. when the maximum allowed height of the hoisting cable of a guiding means is exceeded. In contrast to the variants of a lifting device known from the prior art, it is not necessary here to switch off all winches in case of need, but exactly one winch can specifically be switched off.
To achieve even greater safety, it is expedient that the control unit is configured such that before commencement of the crane operation the individual actuation of each assigned sensor ready for use can be controlled by the controller. Thus, it is ensured that it is clearly known to the control unit which winch performs a hoisting task at which point. This simplifies in particular the separate actuation of the winches by the control unit in case of need.
Since the individual sensors are connected with the control unit in a bilateral exchange of data, it is conceivable that a possible defect of a sensor can be detected by the control unit. For example, when a sensor transmits faulty data or none at all with respect to its mounting position, the control unit will infer a defect of the sensor.
It is also possible that the lifting device of the present disclosure, in particular the sensors for monitoring the guiding means, likewise can be used during the hoisting operations performed for assembly purposes of the lifting device of the present disclosure. As an example, reference is made to the assembly of a lattice boom with the SA trestle or the derrick boom.